Low temperature coal tar derivative insecticide, fungicide, and the like, and process of making the same



Patented Jan. 6, 1942 UNITED. STATES PATENT OFFICE LOW TEMPERATURE COAL TAR DERIVATIVE INSECTICIDE, FUNGICIDE, AND THE LIKE, AND PROCESS OF MAKING THE SAME Caleb Davies, Jr., Ben Avon, 1a., asaignor t5 Pittsburgh Coal Carbonizatlon- Company, Pitts-- burgh, Pa., a corporation of Delaware 4 No Drawing. Application February'lti, 1939,

SerlalNo. 256,726

2 Claims.

erally has a softening point. as determined by the cube-in-water" test, of about 6575 C. This soft pitch is treated withcaustic .soda solu: tion at a temperature of about 95 0., at which temperature the pitch is quite liquid. The caus-- tic soda solution extracts the pitch acids from' the pitch and also other alkali soluble constituents and produces a solution or suspension which 7 is brown in color and which, for convenience,

carbonization of coal. In referring to low. temperature carbonization, we mean carbonization carried out-below a temperature of about 675 C. The temperature which I prefer to employ is about 455C. 1

An important feature of the present invention is the discovery that the low temperature carbonization of coal produces low temperature tar will be referred to herein as brown solution. The pitc permitted to solidify by cooling and the bro n solution is removed. The brown solu-,

tion whic consists at least in part of the sodium salt of the tar acids is usually partially neutralized. with acid, for example sulphuric acid, or with carbon dioxide until it starts to get cloudy.

It is then preferably concentrated by evaporav tion until it contains about 300 grams of organic matter per liter.' The partially neutralized conwhich contains large quantities of high boiling oil boils below about 275C. It will be understood that the low temperature tar obtained by the low temperature carbonization of coal contains light oils, heavy oils and pitch and that by suitable distillation; the oils may be separated from the pitch and the light and heavy oils separated from each other. Furthermore, the distillation of the low temperature tar may be carried to a point such as to produce either soft pitch or hard pitch. In carrying out the present'invention, I may use the high boiling .point oils as herein defined or- I may use the low temperature tar or the soft pitch from the low temperature tar. The tar itself, of course, contains the heavy oils having the tar acids which are particularly suitable for the production of insecticides. The soft pitch resulting from the distillation of the light oils from the tar also contains substantial quantities of the heavy oils. For economical reasons, it is generally advisable toiuse the soft pitch as the starting material for my process of snaking insecticides, since in this way the light oils maybe distilled from the tar and used for other purposes. The invention; therefore, will be described particularly as applied to the treatment of soft pitch obtained from low temperaturetar, by which is meant tar produced by carbonizing coal at a temperature below 675 C.

The soft pitch from low temperature tar gencentratedbrown solution becomes cloudy upon dilution with water. This is probably due to hydrolysis with formation of insoluble acids or resins. This clouding upon dilution can be largely avoided if caustic soda or an emulsifier is added to the concentrated solution before it is dilutedwith water. Suitable emulsifiers are the fatty acids or soaps. Oleic, stearic or other higher fatty acids may be used, but I have found that cheaper fatty acid'materials are satisfactory and, therefore, prefer to employ them, because of theirlower cost. I may use fatty acids obtained from fish oil-or the fish oil material containing the fatty acids. Another suitable material is an impure rosin containing pine fatty acids and abietic acid. The fatty acids are particularly useful as emulsifiers because in addition to their emulsifying action they also neutralize any excess alkali in the brown solution.

The brown solution or the brown solution con taining the emulsifier is a disinfectant, fungicide, insect repellant and insecticide. It reacts with atmospheric oxygen at room temperature to form insoluble matter. As a wood preservative, it has the advantage of penetrating into the wood as an aqueous solution and then depositing a sub- 7 stantially water-insoluble material within the agents. The solution has been used successfully in the treatment of athletes foot.

The disinfectants and the like which have been referred to thus far are used as dilute solutions or suspensions. Where, however, it is desired to produce an insecticide in the form of a solid, it may be obtained in the following manner. The brown solution made according to the method previously described, for example by treating the soft pitch with sodium hydroxide solution, is treated with an acid preferably other than fatty acid, to precipitate dissolved organic matter from the brown solution. This precipitated organic matter will be referred to herein as pitch acids. In carrying out the precipitation any suitable acid may be employed. For example, I may use sulphuric or hydrochloric acid. Where hydrochloric acid is used, thesodium salts of the pitch acids (brown solution) react with the hydrochloric acid to produce sodium chloride and pitch acids. It will be seen that this process involves treating the low temperature tar pitch with an alkali to extract the tar acids thus forming sodium salts of the tar acids and thereafter reprecipitating the acids by the addition of an acid preferably other than a fatty acid.

The softening point of the pitch acids, although 7 higher than that of the pitch from which the brown solution is made, is usually less than 100 C. If the treatment of the brown solution with acid is made at room temperature, the pitch acids take the form of a light brown flocculent precipitate. If made at about 95 0., they form a separate layer of viscous black liquid which cools to a resinous solid. When the pitch acids are freed from soluble salts as by washing them with water, they are superior to brown solution as agricultural insecticides, since they are less injurious to foliage.

Various salts of the previously described pitch acids may be made by adding salts or hydroxidesv of various metals to the brown solution. The salts of metals other than alkalies are substantially insoluble in water and thus salts of the pitch acids may be made by adding salts or hydroxides of metals other than alkalies to the brown solution to precipitate salts of the pitch acids, hereinafter referred to as pitchates," and thereafter separating the pitchates from the solution. Pitchates of calcium, zinc, iron, copper, and mercury have been made by adding salts or hydroxides of these metals to the brown solution. The pitchates are insecticides and fungicides and are more easily dried and stored in finely divided form than the pitch acids which have relatively low softening points. There are indications that the copper pitchate kills some insects which are merely repelled by pitch acids and brown solution. The fungicidal value of certain of the pitchates is superior to that of the corresponding pitch acids or brown solution.

Suspensions and pastes of pitch acids tend to become lumpy in storage, due to the low softening point of the pitch acids. Calcium pitchate suspensions or pastes. on the other hand, due to their somewhat higher softening point, store and handle very well and do not readily become lumpy in storage. However, calcium pitchate suspensions are less effective than the pitch acids against some pests. I have discovered a method by which the advantages of calcium pitchate I phate or other suitable acidic material to the calcium pitchate suspension shortly before using it as a spray material. In this way the acid, for example sulphuric acid, reacts with the calcium of the calcium pitchate to form insoluble calcium sulphate and the pitch acids are liberated from the calcium pitchate. In one instance, of the calcium pitchate suspension was treated with sulphuric acid until the methyl orange end point was reached and then the other 5% of the calcium pitchate suspension was added to insure that no free sulphuric acid was present. It is preferred that the acid used in treating the calcium pitchate be such as to form an insoluble calcium salt, since certain soluble calcium salts, for example calcium chloride, are injurious to foliage under certain weather conditions.

In the processes thus far described, the brown solution was made by treating the soft pitch rethus obtained is of a different character than is obtained by the 'use of sodium hydroxide solution alone. The sodium chloride in the sodium hydroxide solution prevents the solution from extracting certain constituents of the soft pitch which would be extracted by the sodium hydroxde solution alone.

Instead of treating the soft pitch with sodium hydroxide saturated with sodium chloride to producethe modified brown solution, I may first produce ordinary brown solution by extracting the pitch with sodium hydroxide and then saturate the brown solution with sodium chloride to cause a certain portion of the dissolved organic material to separate out from the brown solution. The modified brown solution, however produced, may be used as an insecticide, fungicide or the like or may be treated .in the ways described in connection with the ordinary brown solution, in order to produce pitch acids, salts of the pitch acids or suspensions thereof or any of the other materials referred to.

Whether the ordinary brown solution or the modified brown solution is prepared, it may be made by treating the soft pitch which contains substantial quantities of the high boiling oils previously referred to or by treating the high boiling oils themselves or by treating the low temperature tar containing such high boiling oils. As previously mentioned, the high boiling oils obtained by the low temperature carbonization of coal contain relatively large amounts of the pitch acids or tar acids which by suitable treatment can be converted into condition for use asinsecticides.

I have referred particularly to insecticides or fungicides in describing my invention. These terms are used generically and-not in any narrow srnse. They are intended to'describe products which are useful in killing or repelling insects;

preventing or retarding the growth of fungus, as

be mixed with other insecticides, fungicides or the like.

Although I have described certain preferred materials and procedures, it is to he understood that the invention is not so limited but maybe otherwise embodied or practiced within the scope of the following claims.

I claim:

1. The process of making insecticides, tungicides and the like, which comprises treating: a coal tar material produced by the low temperature carbonization of coal and containing a sub-, stantial quantity of high boiling oil of a character such that not more than 25% of the oil boils below 275' 0., with an alkali-metal hydroxide 5 v solution saturated with alkali-metal chloride.

' and separating the alkaline solution.'

adding a saturated solution of alkali-metal chloride to the alkaline solution to cause a portion of the dissolved organic material to separate from the material, and separating the solid material and solution.

CALEB DAVIES, Jan 

